Catless downpipes are always going to yield better performance gains. We are actually running a group buy on the AR Design N55 4" downpipes right now for those of you who are interested in picking up a set!!

Catless downpipes are always going to yield better performance gains. We are actually running a group buy on the AR Design N55 4" downpipes right now for those of you who are interested in picking up a set!!

I spoke with Harold at HP Autowerks and he told me there was only a 4 HP difference from the iCarbon cattless vs. catted. I'm leading towards the catted. The catted ones are high flow and I like the idea of not having to take off my DP for service due to code issues....